Device for removing broken taps



Dec. 14, 1954 o. CANTIN 2,696,749

DEVICE FOR REMOVING BROKEN TAPS Filed April 8. 1954 PIC-3.1

' iTNNWWWNWww A mzxaa'aw rg 3 .9 0 x [a M INVENTOR. OSCAR CANT/N A T TO/QNEV United States Patent DEVICE FOR REMOVING BROKEN TAPS Oscar Cantin, Windsor, Conn. Application April 8, 1954, Serial No. 421,919

3 Claims. (Cl. 81-90) The invention relates to a device or tool for removing broken taps from threaded or partly threaded holes.

A broken tap removing device of conventional form has fingers which can be entered in the grooves of the tap for rotating it in the proper direction for removal. The general object of the present invention is to provide a device of the class referred to wherein the tap engaging fingers may be freely adjusted independently of each other, wherein the fingers may be rigidly clamped in their proper relationship, and wherein after adjustment and clamping the tool has no relatively movable parts.

In the drawing I have shown two embodiments of the invention, but it will be understood that various changes may be made from the constructions shown, and that the draw ng is not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

Fig. 1 is a combined side and longitudinal sectional view of a broken tap removing device embodying the invention.

Fig. 2 is a left end view.

Fig. 3 is a right end view.

Fig. 4 is an enlarged sectional view taken along the line 4-4 of Fig. 1.

Fig. 5 is a fragmentary view similar to Fig. 1 but showing an alternative embodiment of the invention.

6 is a right end view of the device as shown in Fig. 7 is a schematic view showing a broken tap in a hole and showing a device embodying the invention adjusted for removing the tap.

Fig. 8 is a view similar to Fig. 7 but showing the device differently adjusted.

Fig. 9 is another view similar to Fig. 7 but showing a different broken tap and showing the device differently adjusted.

Referring. to the drawing and more particularly to Figs. 1 to 4, a device embodying the invention includes a core member 10 having a generally cylindrical portion 12 and a squared end portion 14, the latter being adapted for engagement by a wrench. The cylindrical portion 12 has a diameter slightly smaller than the internal diameter of the threads of a threaded hole in which there may be a broken tap to be removed. The cylindrical portion 12 of the member 10 is provided with a plurality of equally spaced longitudinal grooves which are open at the ends thereof opposite the wrench engaging portion 14, there ordinarily being four grooves such as 16, 18, 20 and 22. A similar plurality of longitudinal fingers is provided, there ordinarily being four fingers 24, 26, 28 and 30 which fit and are longitudinally adjustable independently of each other in said grooves in the core member. The end portions of the fingers ordinarily project beyond the core member at the last said end thereof. The fingers have exterior faces which constitute the outermost boundaries of the fingers and which conform to a common cylindrical surface concentric with the axis of the cylindrical portion 12 of the core member It), said cylinder having a diameter slightly larger than that of said portion 12, as will be more clearly apparent from Fig. 4 wherein the difference in diameters is exaggerated. The fingers 24, 26, 28 and 30 are of such size and are so arranged that they are adapted to enter the grooves in a broken tap in a threaded hole as hereinafter more fully explained.

A collet is Drovided which surrounds the core member and engages the outer faces of the fingers to clamp said 2 fingers to the core member in longitudinally adjusted positions. The collet means is longitudinally movable and is engageable with the fingers at all positions throughout the length of the core.

Preferably the collet comprises two companion collet members 34 and 36 which surround the core member and the fingers. The members 34 and 36 have threaded engagement at 38 and they have means such as hexagonal portions 40 and 42 for facilitating the turning of one of them relatively to the other. The inner collet member 34 has a central cylindrical hole of approximately the same diameter as the exterior faces of the fingers, said member therefore engaging and fitting said faces. The left or inner end portion of the member 34 is tapered toward the left and said portion is provided with a plurality of equally spaced longitudinal slots 44, 44, resilient tongues 46, 46 being formed between the slots. As shown, there are four slots and four tongues. The outer collet member 36 has its central opening tapered to conform to the taper on the member 34. When the member 36 is turned relatively to the member 34 so as to be moved toward the right, the tongues 46, 46 are flexed inwardly to grip the fingers and to hold them in fixed positions with respect to the core member. When the member 36 is turned for movement toward the left, the fingers are released so as to be freely movable longitudinally. As shown in Figs. 1 to 4, the slots 44, 44 are in register respectively with the fingers so that each tongue engages two fingers. but this particular relationship is only one of many. The member 34 may have any rotative relationship to the core member and the fingers and said fingers will be grinned and held in any relationship. The collet members 34 and 36 are longitudinally movable so as to be engageable with the fingers at any position throughout the length of the core.

The device as shown in Figs. 5 and 6 is very similar to that shown in Figs. 1 to 4, but collet members 48 and 50 are substituted for the members 34 and 36. The members 48 and 50 have or may have the same construction as the members 34 and 36 except that they are generally cylindrical and have knurled surfaces 52 and 54. The knurled surfaces enable the members to be relatively turned bv the fingers of the user without the use of any tools. The relative turning by means of the knurled surfaces will serve to grip the fingers sufiicientlv for most purposes. However. the members 48 and 50 may be provided with flats 56 and 58 for engagement by wrenches when the fingers must be gri ped more firmly than is possible by means of the knurled surfaces.

Figs. .1 and 5 show the several fin ers proiecting to equal extents toward the left and beyond the portion 12 of the core member and they show the collet located with its left end near the proiecting ends of the fingers but nevertheless spaced therefrom. The relationship of the parts as shown is suitable for removing most broken taps, but other relationships are possible as hereinafter explained. With the fingers projecting as shown they can be entered in the grooves of a broken tap and the tap can be removed by rotating the device by a wrench applied to the squared end 14. The collet is as near the ends of the fingers as is possible, consistent with a proper allowance to enable the fingers to reach into the hole for engaging the tap. It will be observed that when the collet is tightened, whether in the position shown in Figs. 1 and 5 or in some other position, all of the parts of the tap removing device are firmly connected with each other, there being no freely movable part which may become detached or which must be manually held in its proper relationship with the other parts.

It will be apparent that in a device embodying the invention the several tap engaging fingers, when unclamped, are freely adjustable relatively to the core member and also relatively to each other. Adjustment of the fingers relatively to each other is very important for enabling the fingers to properly or more effectively engage a broken tap under certain special conditions.

Fig. 7 shows a broken tap A in a partly threaded hole. As frequently happens, the tap has been broken off approximately along a diagonal plane which is shown for the fingers to enter the several grooves in the broken tap to approximately equal extents, it is necessary for the upper finger 2 4 to project to a greater extent than the intermediate fingers 26 and 30 and for the lower finger 28 to project to a lesser extent than the said intermediate fingers; If the fingers all projected to the same extent, only the lower finger might be properly entered in its corresponding tap groove, particularly if there were chips in the grooves tending to resist the entry of the fingers. With the fingers adjusted as shown in Fig. 7, the collet is tightened to firmly clamp the fingers in their adjusted positions, the collet preferably being as close to the ends of the fingers as is consistent with the engagement of the fingers with the broken tap.

Fig. 8 shows a broken tap B in a partly threaded hole. As shown in Fig. 8, there is a chip b which extends into one of the grooves of the tap B in such a way as to prevent the entry of a finger into said groove. When a condition such as shown in Fig. 8 is encountered, one of the fingers such as 30 may be retained with its end substantially flush with the end ofthe core 12, the other fingers 24, 26 and 28 being in projecting positions for entry into the other grooves of the tap. It will be obvious that if the several fingers were connected with each other so that they could be moved only in unison, a chip such as [9 would prevent any of the fingers from entering any of the grooves of the tap.

Fig. 9 shows a tap C which is broken at the outside of the partly threaded hole. When such a tap is to be removed, the fingers may be adjusted so that they all project to the same extent. not have to reach into a hole, the collet can be positioned as shown very close to the ends of the fingers, the fingers thus being supported even more firmly than is possible under the conditions illustrated in the other views.

The invention claimed is:

1. A device for removing a broken tap from a hole that is at least partly threaded, said device comprising a generally cylindrical core member having a diameter less than the internal diameter of the threads of the hole, said core member having a plurality of similar circumaxially spaced longitudinal grooves all open at one end and said core member having a portion at the opposite end engageable by a wrench, a plurality of similar fingers respectively fitting the plurality of grooves in the core member and longitudinally adjustable in said grooves independently of each other so that some or all of them may project beyond the core member at the first said end thereof for'entry into some or all of the grooves of a broken tap, said fingers having outer faces which conform to a common cylindrical surface which is concentric with the core member and has a larger diameter, and a collet surrounding the core member and engaging the outer faces of the fingers to clamp the fingers to the core member in longitudinally adjusted positions.

2. A device for removing a broken tap from a hole that is at least partly threaded, said device comprising a generally cylindrical core member having a diameter Inasmuch as the fingers do .1

less than the internal diameter of the threads of the hole, said core member having a plurality of similar circumaxially spaced longitudinal grooves all open at one end and said core member having a portion at the opposite end engageable by a wrench, a plurality of similar fingers respectively fitting the plurality of grooves in the core member and longitudinally adjustable in said grooves independently of each other so that some or all of them may project beyond the core member at the first said end thereof for entry into some or all of the grooves of a broken tap, said fingers having outer faces which constitute the outermost boundaries of the fingers and which conform to a common cylindrical surface which is concentric with the core member and has a larger diameter, and a longitudinally movable collet surrounding the core member and engageable with the outer faces of the fingers at all positions throughout the length of the core for clamping said fingers to the core member in longitudinally adjusted positions.

3. A device for removing a broken tap from a hole that is at least partly threaded, said device comprising a generally cylindrical core member having a diameter less than the internal diameter of the threads of the hole, said core member having a plurality of similar circumaxially spaced longitudinal grooves all open at one end and said core member having a portion at the opposite end engageable by a wrench, a plurality of similar fingers respectively fitting the plurality of grooves in the core member and longitudinally adjustable in said grooves independently of each other so that some or all of them may project beyond the core member at the first said end thereof for entry into some or all of the grooves of a broken tap, said fingers having outer faces which conform to a common cylindrical surface which is concentric with the core member and has a larger diameter, an inner collet member surrounding the core member and engaging the outer faces of the fingers, said member having longitudinal slots at the end thereof adjacent the first said end of the core member and said member being longitudinally adjustable relatively to the core member and the fingers, and an outer collet member surrounding the inner collet member and having threaded engagement therewith for relative longitudinal adjustment, said outer collet member upon longitudinal adjustment serving to flex the portions of the inner collet member between the slots thereof so as to clamp said fingers to the core member in longitudinally adjusted positions.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 574,077 Sellers Dec. 29, 1896 702,011 Kinwall June 10, 1902 1,331,366 Pesa Feb. 17, 1920 2,448,805 Ingram Sept. 7, 1948 2,539,532 Daniels Jan. 30, 1951 

